I have a question with regards to NMOS's.. I am aware that the NMOS switches from Cut-off to Triode/Saturation once the Vgs is larger than the Threshold Voltage(which is a process parameter).

Now my question is as follows. How is it possible to alter the switching voltage such that the NNOS can be configured to switch on at a set voltage level? Basically, I want the NMOS to switch On at a voltage of say 2 volts (rather than Vt).

The FET will have Vgs threshold stated as some min/max value such as 1V to 3V, and this will not change (unless you select a different FET, which will still have a min/max spread) -- due to the process as you noted. Therefore in using it as a switch, you would want to make sure to apply more than 3V (using above numbers) to the gate to make sure it is fully on -- 2V would not really suffice.

One way to overcome this is to use a +5V comparator with the minus (-) side referenced at your desired voltage (say +2.0V), with the input signal on the plus (+) side. While the input signal is less than +2V the comparator outpu will remain low and the FET off. Whenever your input is above +2.0V reference, the comparator out would drive the FET gate sufficiently to saturation (and, for the most part, indiscriminately of which FET you choose).